HSC Survey Results

German Bank Survey # 4 Results from 15/09/2024

Survey Details

6 commercial purse seiners conducted this fishing survey on 15/09/2024 starting at 20:00:00.

All vessels ran two transects in the German Bank box and two transect in the Seal Island Box.

There was a plankton tow and replicate conducted and CTD cast by Lady Melissa.

No tags were applied during this survey.

Samples were obtained for target strength estimation.

Acoustic Equipment

Each vessel was equipped with a Simrad ES38-18/200-18C combi (2-in-1) transducer prior to the survey that contains a 38kHz split beam and 200 kHz single beam transducer. Data was logged to the computer hard-drive for post-processing. All participating boats were calibrated on 38kHz before the survey.

Survey Results

Main Results

The results are subject to change as DFO will re-evaluate data editing, area estimation and apply a target strength.

Preliminary biomass prediction for German Bank using standardized parallel transects is 24,824mt, and with turnover applied 21,033mt. The preliminary biomass estimate for Seal Island is 1,369mt.

Transect Details

Table 1: Transect Details
Vessel Transect # Date/Time Start Date/Time End Start Lon Start Lat End Lon End Lat Location Distance (km) Speed
C1 T01 2024-09-15 19:43:03 2024-09-15 22:08:52 -66.491 43.567 -66.490 43.237 GB 38.94 8.65
C1 T02 2024-09-15 22:42:33 2024-09-16 01:11:06 -66.353 43.235 -66.355 43.565 GB 38.62 8.42
C1 T03 2024-09-16 01:43:06 2024-09-16 03:30:55 -66.231 43.502 -66.230 43.248 GB 29.83 8.96
C1 T04 2024-09-16 03:45:06 2024-09-16 05:35:52 -66.174 43.248 -66.175 43.505 GB 30.30 8.86
FM T01 2024-09-15 20:33:29 2024-09-15 23:05:03 -66.470 43.569 -66.470 43.234 GB 37.99 8.12
FM T02 2024-09-15 23:41:28 2024-09-16 02:07:12 -66.333 43.235 -66.332 43.567 GB 37.55 8.35
FM T03 2024-09-16 02:39:46 2024-09-16 04:21:35 -66.221 43.504 -66.220 43.249 GB 28.78 9.16
FM T04 2024-09-16 04:36:30 2024-09-16 06:26:39 -66.163 43.247 -66.164 43.505 GB 29.25 8.60
LB T01 2024-09-15 19:29:22 2024-09-15 22:08:37 -66.401 43.567 -66.401 43.235 GB 38.07 7.74
LB T02 2024-09-15 22:49:17 2024-09-16 01:18:27 -66.265 43.233 -66.263 43.566 GB 37.97 8.25
LB T03 2024-09-16 01:47:21 2024-09-16 03:33:37 -66.192 43.502 -66.192 43.247 GB 29.02 8.85
LB T04 2024-09-16 03:53:31 2024-09-16 05:38:16 -66.135 43.249 -66.136 43.504 GB 29.07 8.99
LJ T01 2024-09-15 19:40:03 2024-09-15 22:09:06 -66.423 43.568 -66.424 43.233 GB 37.38 8.13
LJ T02 2024-09-15 22:45:14 2024-09-16 01:11:09 -66.286 43.234 -66.286 43.567 GB 37.10 8.24
LJ T03 2024-09-16 01:39:53 2024-09-16 03:27:10 -66.202 43.504 -66.201 43.250 GB 28.32 8.55
LJ T04 2024-09-16 03:43:24 2024-09-16 05:35:52 -66.144 43.248 -66.144 43.502 GB 28.28 8.15
LM T01 2024-09-15 19:26:36 2024-09-15 21:55:41 -66.374 43.572 -66.378 43.233 GB 38.51 8.37
LM T02 2024-09-15 22:31:28 2024-09-16 00:58:51 -66.241 43.233 -66.239 43.568 GB 37.81 8.31
LM T03 2024-09-16 01:22:58 2024-09-16 03:14:25 -66.182 43.501 -66.182 43.246 GB 28.82 8.38
LM T04 2024-09-16 03:32:00 2024-09-16 05:23:38 -66.124 43.249 -66.125 43.500 GB 28.36 8.23
MS T01 2024-09-15 19:34:10 2024-09-15 22:10:57 -66.448 43.566 -66.447 43.233 GB 38.71 8.00
MS T02 2024-09-15 22:50:16 2024-09-16 01:17:53 -66.308 43.235 -66.309 43.566 GB 38.37 8.42
MS T03 2024-09-16 01:50:17 2024-09-16 03:28:35 -66.211 43.502 -66.211 43.247 GB 29.21 9.63
MS T04 2024-09-16 03:47:05 2024-09-16 05:40:59 -66.153 43.248 -66.156 43.508 GB 30.04 8.54

Survey Summary

Table 2: Acoustic Survey Results
Vessel Transect No.  Target Strength (db/kg) Mean Sa (/m2) Biomass Density (kg/m2)
LM T01 -35.5 -43.574 0.156
MS T01 -35.5 -49.781 0.037
LB T01 -35.5 -49.805 0.037
FM T01 -35.5 -49.974 0.036
LB T02 -35.5 -51.252 0.027
MS T02 -35.5 -52.860 0.018
LJ T01 -35.5 -53.498 0.016
FM T02 -35.5 -54.592 0.012
MS T04 -35.5 -54.949 0.011
FM T04 -35.5 -56.064 0.009
C1 T01 -35.5 -56.738 0.008
LB T04 -35.5 -57.140 0.007
LJ T04 -35.5 -57.653 0.006
LM T04 -35.5 -57.749 0.006
MS T03 -35.5 -57.882 0.006
C1 T02 -35.5 -58.323 0.005
LJ T02 -35.5 -59.137 0.004
C1 T04 -35.5 -60.834 0.003
FM T03 -35.5 -61.311 0.003
LM T02 -35.5 -61.558 0.002
LM T03 -35.5 -61.867 0.002
LB T03 -35.5 -62.480 0.002
LJ T03 -35.5 -64.194 0.001
C1 T03 -35.5 -65.250 0.001
Note:
Transects are listed from greatest to least backscatter.
Table 3: Survey Summary Table
Layer Target Strength Area (km2) Mean Sa Density (kg/m2) Biomass (tons) Percent Area Percent Biomass Standard Error (tons) Standard Error (%)
German Bank -35.5 826.1781 -50.722 0.0299 24,824.032 74.2 94.8 9,953.95 40.10
Seal Island -35.5 287.0035 -58.715 0.0048 1,368.945 25.8 5.2 268.03 19.58

Greatest Biomass Densities

A snip from the transect with the greatest biomass density (kg/m2)

A snip from the transect with the greatest biomass density (kg/m2)

The single point with the largest biomass density (kg/m2) was recorded by LM, at the following location:

The transect with the greatest average biomass density (kg/m2) was recorded by LM, at the following location:

Annual Summaries

Table 4: Annual Comparison Table
Current Year
Previous Year
Ground Survey Number Survey Date HSC Estimate HSC Turnover Adjusted Survey Date HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
German Bank 1 2024-08-04 12,233 12,233 2023-08-06 2,687 2,687 2,021 2,021
Seal Island 1 2024-08-04 45,930 NA 2023-08-06 1,205 NA 929 NA
German Bank 2 2024-08-18 14,054 11,668 2023-08-20 4,930 4,406 3,282 2,887
Seal Island 2 2024-08-18 6,285 NA 2023-08-20 1,918 NA 897 NA
German Bank 3 2024-09-02 15,499 12,639 2023-09-03 9,959 8,901 8,372 7,660
Seal Island 3 2024-09-02 3,770 NA 2023-09-03 2,063 NA 1,099 NA
German Bank 4 2024-09-15 24,824 21,033 2023-09-13 16,266 13,203 15,011 12,498
Seal Island 4 2024-09-15 1,369 NA 2023-09-13 5,636 NA 4,045 NA
German Bank 5 NA NA NA 2023-09-27 15,242 11,360 13,503 9,978
Seal Island 5 NA NA NA 2023-09-27 53,844 NA 42,269 NA
German Bank 6 NA NA NA 2023-10-11 23,614 20,057 26,563 23,390
Seal Island 6 NA NA NA 2023-10-11 15,261 NA 14,381 NA
German Bank 7 NA NA NA 2023-10-24 11,184 5,502 13,033 6,803
Seal Island 7 NA NA NA 2023-10-24 1,006 NA 1,087 NA
Table 5: Annual Summary Table
Year Ground HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
2023 German Bank 83,882 66,116 81,785 65,237
2023 Seal Island 80,933 NA 64,707 NA
2024 German Bank 66,610 57,573 NA NA
2024 Seal Island 57,354 NA NA NA

Tagging, Plankton, and CTD Data

Summary map

Vessel Tags

Plankton Data

Tow Summary Table

Tow 1
Tow 2
Base Details
Vessel Lady Melissa Lady Melissa
Set Number GB2024-05 GB2024-06
Ground GB GB
Date 15/09/2024 15/09/2024
Wind Direction (km/h) W W
Swell (m) 0 0
Air Temp (c) 18 18
Tow Details
Tow Start 18:47:00 19:06:00
Tow End 18:57:00 19:16:00
Start Lat 43.56500 43.55183
End Lat 43.55317 43.54083
Start Lon -66.35933 -66.35083
End Lon -66.36383 -66.35100
Avg Tow Depth (m) 4.806753 4.842088
Speed 5.1 4.0
Heading 198 180
Tide Direction with against
Other Data Collection
Flow Start 725125 799198
Flow End 788900 862762
No. Revolutions 63775 63564
Distance (m) 1713.826 1708.155
Volume 5383.983 5366.170
Secchi Disappear (m) 7 7
Secchi Reappear (m) 6 6

Tow Depth Profiles

Plankton tow depth profile #1

Plankton tow depth profile #1

Plankton tow depth profile #2

Plankton tow depth profile #2

The first tow is GB2024-05, which was with the tide and had an average depth of 4.8067531m. The second tow is GB2024-06, which was against the tide and had an average depth of 4.8420878m.

Captured plankton

Captured plankton from the surface tows

Captured plankton from the surface tows

CTD Data

CTD depth profiles for all 2024 German Bank surveys so far.

Sea surface temperatures

Annual average sea surface temperatures (SST) for German Bank.

Vessel Performance

Speed

Average vessel speed was 8.5. This is above the 8 knot requirement; vessels are urged to slow down to prevent backscatter noise from interfering with the acoustic data.

The speed for each transect are rudimentary and are calculated based on distance. If a significant amount of distance is cut, the speed will appear slower.

Distance

No significant distance was cut from the planned lines; vessels covered the planned area well.